Apparatus for determining the opacity of paper and other materials



Aug. 2, 1938. o. MAASS ET AL APPARATUS FOR DETERMINING THE OPACITY OF PAPER AND OTHER MATERIALS Filed Oct. 16, 1935 51 1 INVENTORS 1 one was ROllAlD-B-RICHARDSON a @fmmw AT TORNEY aiented Aug. E38

APPARATUS FOR DETER I"l" n G THEE @IPAC- ITY OF PAPER- AND o'rnnn Maren Otto Maass, Montreal,

Richardson, Oshawa, Ontario,

Quebec, and honaid E.

rum-I assignors to The Canadian Pulp and Paper Research Corporation, Montreal, Quebec, Canada Application October 1c, 1935, Serial No. 45,294

dclaims.

This invention relates to apparatus for determining the opacity of paper and other materials.

The object is to provide a generally improved apparatus of the type in which light sensitive cells are balanced against each other so that the current modifying effect obtained by interposing a sample of the paper or other material between one of the cells and a light source may be readily determined as an accurate measure of the opacity of the sample. v

Proceeding now to a more detailed description reference will be had to the accompanying drawing in which Figure 1 is a view, in vertical section, of one form of apparatus adapted to be used in accordance with this invention.

Figure 2 is a top plan view of the apparatus appearing in Figure 1.

Referring more particularly to the drawing," designates a casing mounted on a suitable supporting structure t. This casing contains arotary carrier I fixed to the'upper end of a hollow shaft 8 which rotates in self-aligning ball bear- ,ings 9 fitted in a tubular portion iii of said casing. A pulley II is fixed to shaft 8 below the casing 5 and is driven through belt i2 by means of an electric motor (not shown).

The carrier I comprises spaced upper and lower plates l3 and I4 joined together by a hub l5 which is fitted on the upper portion of shaft 8. The carrier is clamped in place between the upper shaft bearing 9 and a suitable clamping nut IS. A pair of photronic cells H are placed on the lower carrier plate l4 with their centres 180 apart, the

, upper portions of the cells being fitted in suitable openings l8 formed in the upper carrier plate l3.

One half of the top opening 5b of easing 5 is permanently closed off by a stationary, semi-circular, shutter plate l9 which is fastened to the casing rim 50. by bolts or other suitable fastening means. A box 2|, containing a photronic cell 22, is fastened to the upper surface of shutter plate l9. This box is provided with a hinged cover 23 having an opening 24 which, in the closed position of the cover, lies directly above the cell 22.

An adjustable, semi-circular, shutter plate 25 is arranged in the casing 5 between the stationary shutter plate l9 and the carrier I. Plate 25 is 0 fastened, by screws 26, to a carrier ring 21. This ring is rctatably supported on a ledge 28 of the casing by means of ball bearings 29 and is adapted to be rotated in a horizontal plane by a friction drive roller 30 fixed to the inner end of a shaft 3 I This shaft is journalled in a suitable bearing .33

and carries a hand wheel 34 at its outer end. By turning the hand wheel. 34 the movable shutter plate 25 may be adjusted to close of! more or less of that portion of the top opening of casing 5 which is left uncovered by the stationary shutter plate M. This adjustment of plate 25 is resorted to in order to vary the length of time that the cells I! are exposed to the light source 36 during each revolution of the carrier .1. r

The movable cells I! are connected, in parallel 'witheach-other, to the operating coil 3i] of a galvanometer 38, the remaining coil 39 of which is connected in series with the stationary cell 22. As here shown the terminals 40 and 4! of cells Ill? are connected, by conductors 44 and 45, to terminals 46 and 47 carried at the lower end of shaft B. These terminals 46 and 41 dip into the legs 43 and 49 of a pairof concentrically arranged mercury containers 50 and 5i and are thus connected to terminals 52 and '53 which are arranged to dip into the remaining legs 54 and 55 of said containers. Conductors 56 and 57 connect the terminals 52' and 53 to opposite ends of the galvanometer coil 31. The conductors connecting the cell 22 in series with the galvanometer coil 39 are shown at 58 and 59. With this method of connecting the cells the current generated in cells I! is opposed to the current generated in cell 22 so that the position 01' the galvanometer pointer 60 is dependent upon the relative strengths of the opposed currents.

In the use of this apparatus the light passing through the cover opening 24 of box 2| generates a. current in cell 22 which tends to deflect the galvanometer pointer 60 in one direction. At the same time the cells H are being successively exposed to light by rotation of the carrier l with the result that the currents generated in these cells tend to deflect the galvanometer pointer in the opposite direction. It will be assumed that the movable shutter 25 lies wholly beneath the stationary shutter l9 and that the light striking cells i1 is more intense than that striking the cell 22 or that cell 22 is weaker than either of cells ll. Under these circumstances the currents generated in cells i1 will be sufliciently stronger than that generated in cell 22 to produce a corresponding deflection of the galvanometer pointer in the last mentioned direction. If, now, the movable shutter plate 25 is rotated to partly close oil that .portion of easing opening 5b,which is not covered by the shutter plate i9, then the time during which the rotating cells II are exposed to the light source 36 is decreased and produces a corresponding decrease in the strength of the current generatedinsaidcells. rromthis itwillbe seen that, by appropriate adjustment of the shutter plate 25, of time during which the cells iI' are exposed to light may be regulated so that the currents generated in these cells will exactly balance that generated in cell 22, in which case the shows no deflection. when this condition is achieved the area of the opening through which the cells II are exposed to light is proportional to the angle, assumed as X, between the points J and K! the fixed and adjustable shutter plates. The ring 21 is provided with a.

vernier scale 02 so that this angle may be readily determined for each position of the shutter 25.

when the shutter II has been adjusted so that thegalvanomcter pointer is at zero the apparatus is set for use 'in determining the opacity of paper or other materials. A sample to be tested,

is then placed in the box 2| between the cell a andthe'cover 23 so that it intercepts the light passing through the cover opening II. The re- Y, then the ratio of the light received bythe revolving cells il, before and after introduction of the sample, is 1 Hence, the light intensities,

received by cells n, before and after introduction of the sample, are also in the ratio of 'ihe'transmittance. i. e. the fraction of the incident light passing through the sample is The obtained in accordance with the invention may require a slight correction owing to the change in the angle of incident radiation on cell 22 caused by the interposition of the sample whose opacity is to be measured. Such correction may be made by simple methods known to ,the art, for example, by simple calibration with samples of known capacity.

Having thus described what we now consider to be a preferred embodiment of this invention it will be understood that various modifications mayberesortedtowitninthescopeoitheappended claims. It is possible, for example, to useamodifledformofthe apparatusinwhich the stationary cell 22 is balanced against a single cell mounted on the rotatable can'ier I. In this case the movable cell would be stronger than the stationary cell. to permit the opposed currents oi the cells-to be exactly balanced by appropriate adjustment of the movable shutter II or some equivalent means. It is also feasible to provide the carrier I with a greater number of parallel connected cells than that shown in the 1. Apparatus for determining the opacity of paper and the like, comprising a light source, a

pair of photovoltaic cells positioned to receive light from said source, electrically operable indicating means, circuits connecting said indicating means and said cells in a manner to oppose the cell currents produced by the action of light from said source to register in said indicating means difierences in the strengths of the opposed currents, a light intercepting member disposed between said light source and one of said cells and having an aperture therein, a rotary carrier behind said member, one of said cells being mounted eccentrically on said carrier behind said member, means for rotating said carrier to move the cell thereon periodically across the aperture at a. predetermined speed, and a cover adjustable over said aperture to vary the effective area thereof.

2. Apparatus for determining the opacity of paper and the like, comprising a light source, a plurality of photovoltaic cells positioned to receive light from said source, one of said cells being fixed, electrically operable indicating means, a circuit connecting said fixed cell and the indicating means, a circuit connecting the other cells and the indicating means in opposition to said first circuit whereby said indicating means registers difierences in the strengths of the currents produced in said fixed cell and in the other cells by action of light from said source, a stationary light intercepting member disposed between said light source and said other cells and having an aperture, a carrier mounted for rotation behind said member, said other cells being supported eccentrically on said carrier, means for rotating said carrier whereby the cells thereon are periodically successively moved across said aperture at a predetermined speed, and a cover adjustable over said aperture to vary the effective area thereof.

3. Apparatus for determining the opacity of paper and the like, comprising ,a light source, a plurality of photovoltaic cells positioned to receive light from said source, one of said cells being fixed, electrically operable indicating means, a circuit connecting the fixed cell and the indicating means, a circuit connecting the other cells and the indicating means in opposition to said first circuit whereby said indicating means registers differences in the strengths of the currents produced in said fixed cell and in the other cells by action of light from said source, a rotary carrier supporting eccentrically said other cells, means for rotating said carrier to cause travel of the cells thereon within the range of said light source, adjustable light intercepting means between said light source and the carrier cells, and means for adjusting said intercepting means to .vary the extent of exposure of said carrier cells to the light from said source.

4. Apparatus as set forth in claim 3, in which the light intercepting means comprises a casing enclosing the rotary carrier and the cells thereon, a stationary plate covering a portion only of the top of the casing, and a cover adjustable relatlve to said plate over the remaining portion of the top of the casing.

RONALD E. RICHARDSON. 

